CN107425533A - Synchronous inverter is incorporated into the power networks situation profit guiding method during a kind of Voltage unbalance - Google Patents
Synchronous inverter is incorporated into the power networks situation profit guiding method during a kind of Voltage unbalance Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/40—Synchronising a generator for connection to a network or to another generator
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase networks
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Abstract
It is incorporated into the power networks situation profit guiding method the invention discloses synchronous inverter during a kind of Voltage unbalance.Tendency Prediction is combined with sharp guiding method first and applies to grid-connected synchronous inverter, ensures that distributed power source can continually and steadily be incorporated into the power networks under the conditions of voltage on line side imbalance.Synchronous inverter is incorporated into the power networks modeling during including unbalanced source voltage；Super real-time situation prediction based on negative-sequence current；Grid-connected three parts of synchronous inverter situation profit guiding method during unbalanced source voltage.Using the synchronous inverter of simulation synchronous generator operation principle, when voltage on line side occurs uneven, information acquisition unit first extracts unbalanced component, data processing and Situation Assessment are carried out again, advanced prediction is carried out to inverter output current situation, the active decision that negative phase-sequence controller is then carried out on the basis of Tendency Prediction realizes that situation profit leads function, can effectively suppress negative-sequence current, current unbalance factor is reduced, system is continued stable operation in unbalanced source voltage.
Description
Technical field
The present invention relates to when micro-grid system monitoring, analysis and a kind of control technology field, more particularly to Voltage unbalance
Synchronous inverter is incorporated into the power networks situation profit guiding method.
Background technology
As regenerative resource permeability improves constantly, power system gradually generates electricity to distributed power generation direction from centralization
Development, most of distribution type renewable energies are needed by DC/AC converters（Inverter）Electric energy is conveyed to power network, to realize friend
It is good grid-connected, therefore combining inverter is the important component for realizing that distributed power source is grid-connected, common distributed interface inversion
The control method of device has droop control, constant voltage constant frequency control, PQ controls etc., and above-mentioned control strategy has fast excellent of dynamic response
Point, but due to lacking rotary inertia, a large amount of grid-connected inertia for having slackened power network, influence the stability of a system；Using the synchronous hair of simulation
The operation principle of motor, synchronous inverter devise virtual rotation inertia, in the case where not changing the existing method of operation of power network,
Distributed energy close friend can be made to be connected to the grid, therefore synchronous inverter realizes that the grid-connected application prospect of distributed power source is good.
Unbalanced grid faults or asymmetrically placed load failure cause unbalanced source voltage, are the common failures of power network, when
When line voltage occurs uneven, synchronous generator inputs negative-sequence current to power network, exacerbates unbalanced source voltage, reduces
The stability of power network, and simulate the synchronous inverter of synchronous generator there is also same problem.When grid voltage amplitude is uneven
When degree reaches 2%, inverter output current degree of unbalancedness rises to 5 times during balance, have impact on the stabilization of whole system operation
Property, therefore it is synchronous inverter urgent problem to be solved to reduce negative-sequence current degree of unbalancedness；It is first in order to solve the problem present invention
Secondary be combined Tendency Prediction with sharp guiding method applies to grid-connected synchronous inverter, when distributed power source uses synchronous inverter control
When system is incorporated into the power networks, advanced prediction is carried out to inverter output current by Situation Forecast Technique, electric current situation is predicted in advance and becomes
Change information, the threshold value that then imposed a condition on the basis of Tendency Prediction makes negative phase-sequence controller carry out active decision to realize situation profit
Function is led, can effectively suppress the degree of unbalancedness of negative-sequence current in real time, makes system to continue to keep steady under the conditions of Voltage unbalance
Fixed operation.
Tendency Prediction and profit are led and applied in micro-capacitance sensor, emphasis is to realize the sensed in advance to self-operating situation, is led to
The reasonable using grid-connected with close friend of regenerative resource can be effectively facilitated by crossing following development trend of prediction；Again in the base of sensed in advance
System future is assessed on plinth, realized by taking corresponding measure to system mode towards beneficial direction
Dynamic flexible adjusts and control, and situation profit guiding method is applied in micro-capacitance sensor can be by the control strategy of synchronous inverter come real
Existing system favo(u)red state is oriented to.
The content of the invention
During for unbalanced source voltage, synchronous inverter inputs negative-sequence current to power network, aggravates unbalanced source voltage,
Reduce operation of power networks stability the problem of, the invention provides synchronous inverter during a kind of Voltage unbalance be incorporated into the power networks situation profit
Guiding method, the purpose is to carry out advanced prediction to inverter output current using Situation Awareness method, with reference to current unbalance factor
Situation Assessment result, by imposing a condition, threshold value controls the switching of inverter negative phase-sequence controller to realize that situation profit leads function,
So as to suppress negative-sequence current in real time, current unbalance factor is reduced.
To achieve the above object, the present invention adopts the following technical scheme that：It is incorporated into the power networks control system including synchronous inverter：
Synchronous inverter control module, inverter output end positive-negative sequence current/voltage decomposition unit, the positive and negative sequence voltage of grid side power end
Resolving cell；The Tendency Prediction method of system parameter during Voltage unbalance：Inverter output end current acquisition module, electric current situation
Identification and evaluation module, electric current Tendency Prediction model；Systematic thinking way is snobbish during Voltage unbalance leads execution method：Current unbalance factor
Situation display unit, situation profit lead the setting of Rule of judgment, the decision-making technique of condition threshold control negative phase-sequence controller switching.
Synchronous inverter is incorporated into the power networks situation profit guiding method during a kind of Voltage unbalance, comprises the following steps：
1）When Voltage unbalance occurs for grid side, synchronous inverter output voltage is not synchronous with grid side voltage, then inverter
To power network input current, grid side voltage and inverter output voltage, Current Decomposition are positive sequence and born using symmetrical component method
Order components, measurement obtain the amplitude and phase information of positive and negative sequence component；Simulation synchronous generator principle establishes positive sequence Synchronization Control
System and negative phase-sequence synchronous control system, wherein positive sequence synchronous control system realize the transmission of power, and negative phase-sequence synchronous control system exists
The regulation of voltage is carried out during Voltage unbalance；
2）During in Voltage unbalance, synchronous inverter is incorporated into the power networks, inverter is exported by current acquisition module first
Electric current carries out current situation extraction conductTThe status information at moment, secondly to extractionTTime data carries out situation identification with commenting
Estimate, that is, judge whether this group of data uneven trend occur（WithTThe current data being collected into before moment is compared analysis）
And data are pre-processed, judge data characteristic, forecast model is finally determined according to Situation Assessment result, then carry outT+When 1
The Tendency Prediction at quarter；
3）It will predict what is obtainedT~T+The actual value that the electric current situation value of 1 period exports as inverter, carry out coordinate transform and
The extraction of symmetrical components, and the situation of the value of calculating current degree of unbalancedness, i.e. current unbalance factor is presented；
4）Presented by the situation of current unbalance factor, threshold value setting is carried out to degree of unbalancedness, whenT~T+The a certain moment in 1 periodT k Degree of unbalancedness when exceeding this threshold value, the condition switch action of negative phase-sequence control system carries out active decision, negative phase-sequence controller
Start to act on, make the negative sequence voltage of synchronous inverter synchronous with the recovery of electrical network negative phase-sequence voltage, so as to suppress synchronous inverter output
Negative-sequence current, reduce current unbalance factor, ensure that whole system continues stable operation.
Synchronous inverter is incorporated into the power networks situation profit guiding method during above-mentioned Voltage unbalance, it is characterised in that：The step
1）In, for synchronous inverter according to synchronous generator operation principle, there is provided virtual rotation inertia, subtracts its dynamic responding speed
It is slow, to maintain the inertia of power network then to realize inverter side and grid side voltage and frequency so as to maintain the stable operation of power network
Synchronous operation, wherein synchronous inverter output end voltage equation expression formula is：（In formula：φFor rotating excitation field axis and the axis angle of A phases,M f For excitation mutual inductance,ɷFor rotor velocity,i f For exciting current）, inversion
The stator terminal phase voltage of device is：（In formula：R l WithL l For stator winding coil resistance and inductance,iFor three-phase
Stator current）；Run in equilibrium conditions when whole system starts, when line voltage occur it is uneven when, synchronous inverter to
Power network input currenti, i.e.,（In formula：R g WithL g For grid side line resistance and inductance,v g For line voltage,ɷ 0
For electrical network angular frequency）, line voltage and inverter output voltage, electric current can be analyzed to positive sequence, negative sequence component（Because of synchronous inverter
There is no the neutral conductor can not consider zero-sequence component）, then voltage unbalance factor be：, current imbalance
Spend and be：；Simulation synchronous generator principle establishes positive sequence synchronous control system and negative phase-sequence is same
Control system is walked, wherein positive sequence synchronous control system is adjusted to track by the voltage and frequency for aligning sequence controller output
Line voltage and frequency, so as to realize the transmission of active power and reactive power, do not have in negative phase-sequence synchronous control system running
There is the transmission of power, inverter output negative sequence voltage and electrical network negative phase-sequence voltage synchronous are only kept, by formulaCan
Know, whenu - =v g - When, havei - =0, this process is without influence on the operation of positive sequence synchronous control system, respective independent operating, therefore
Synchronous inverter suppresses in unbalanced source voltage to negative-sequence current, makes it that electricity can be achieved in operational envelope
Synchronous inverter is incorporated into the power networks during net Voltage unbalance.
Synchronous inverter is incorporated into the power networks situation profit guiding method during above-mentioned Voltage unbalance, it is characterised in that：The step
2）In, current situation extraction is carried out to inverter output current by current acquisition module and is used asTThe status information at moment, note
{i 1,i 2,...,i n BeTThe current time sequence at moment, because grid side Voltage unbalance has three kinds of situations, i.e. voltage magnitude
Imbalance, unbalance in phase, amplitude and phase are all uneven, therefore the uneven situation of inverter output current also has three kinds,
In order that prediction effect is preferable, forecast model is according to three kinds of uneven situations respectively using chaos time sequence method, BP nerve nets
Network predicted method and wavelet neural network predicted method carry out Tendency Prediction；From the foregoing, it will be observed that the electricity to extraction is needed before being predicted
Stream time seriesi 1,i 2,...,i n Carry out situation identification and assessment, the i.e. unbalance factor of Cutoff current time series（It is each pre-
Survey the characteristic quantity of model）, it is predicted again after determining forecast model.
Synchronous inverter is incorporated into the power networks situation profit guiding method during above-mentioned Voltage unbalance, it is characterised in that：The step
3）In, it will predict what is obtainedT~T+1 period electric current situation valuei’(t),t=1,2,...,nIt is the electric current of future-state as inverse
Become device output current actual value, and carry out the extraction of symmetrical components, corresponding current unbalance factor is calculated, by electric current not
The situation of the degree of balance is presented to determine its development trend i.e. guiding of situation.
Synchronous inverter is incorporated into the power networks situation profit guiding method during above-mentioned Voltage unbalance, it is characterised in that：The step
4）In, byUnderstand, the degree of unbalancedness of grid side voltage directly influences the imbalance of inverter output current
Degree, by the system points of common connection of International Electrotechnical Commission's clear stipulaties（PCC）Normal voltage degree of unbalancedness permissible value is 2%, short
When no more than 4%, therefore when carrying out threshold value setting to current unbalance factor, can be carried out according to the degree of unbalancedness of grid side voltage
Primarily determine that, i.e.,IUF=k 1 *VUF（In formulak 1For proportionality coefficient and）；If the time of forecast model ist y ,
Because synchronous inverter is provided with virtual rotation inertia, slow down its dynamic responding speed, so during in the presence of a habitual response
Betweenτ v ≈K 0 /(ω*D q )（In formulaD q =-ΔQ/ΔVFor the sagging coefficient of voltage,ωFor electrical network angular frequency,K 0For time scale system
Number）, therefore work asT~T+The a certain moment in 1 periodT k Degree of unbalancedness exceed threshold value, when negative phase-sequence controller carries out active decision, its
The actual act time should be predicted time and the habitual response time for subtracting model at the moment, i.e. decision-making actuation time isT 0 =T k -t y -τ v , so just can guarantee that negative phase-sequence controller effectively acts on, to realize that effective situation profit is led, it is steady to ensure that whole system continues
Fixed operation.
Method proposed by the present invention is to apply to first in the micro-capacitance sensor of synchronous inverter control, for solving line voltage
Existing relevant issues under the conditions of imbalance.
The beneficial effects of the present invention are：The combining inverter of the present invention is controlled using synchronous inverter, in line voltage
It can realize that distributed electrical source transmits to the power of grid side under the conditions of imbalance, it is synchronous when line voltage occurs uneven
Inverter can input negative-sequence current to power network, aggravate the imbalance of power network, now by inverter output current, voltage and power network electricity
Pressure resolves into two symmetrical positive and negative order components, establishes positive sequence synchronous control system and negative phase-sequence synchronous control system, positive-negative sequence electricity
Controller corresponding to pressure and electric current input；Positive sequence synchronous control system realizes the tracking of power, ensures the grid-connected of distributed power source
Operation；Effect of the negative phase-sequence synchronous control system to negative-sequence current, it is combined using Tendency Prediction with sharp guiding method：Adopted using electric current
Collect unit and situation extraction is carried out to inverter output current, then situation identification is carried out to extraction data and assessed, that is, judge the group
Whether data there is unstable trend（WithTThe current data being collected into before moment is compared analysis）And data are carried out pre-
Processing, judges data characteristic, finally determines forecast model according to Situation Assessment result, then carry outT+The Tendency Prediction at 1 moment；Will
What prediction obtainedT~T+The actual value that the electric current situation value of 1 period exports as inverter, carry out coordinate transform and symmetrical components
Extraction, and the value of calculating current degree of unbalancedness, presented by the situation of current unbalance factor, carrying out threshold value to degree of unbalancedness sets
It is fixed, set condition switch to make corresponding judgement, negative phase-sequence controller is carried out active decision；When negative phase-sequence controller starts effect,
Negative-sequence current is inhibited, and negative-sequence current degree of unbalancedness decreases, and is maintained in threshold range, enables the system to safety and stability
Operation.
Brief description of the drawings
Fig. 1 is present system overall structure frame diagram.
Fig. 2 is the inventive method flow chart.
The phase space plan of synchronous inverter output current wave when Fig. 3 is power grid operation of the present invention.
The phase space plan of synchronous inverter output current wave when Fig. 4 is grid voltage amplitude imbalance of the present invention.
Inverter output current actual value and predicted value simulation waveform pair when Fig. 5 is grid voltage amplitude imbalance of the present invention
Than figure.
Embodiment
The present invention is further illustrated with reference to the accompanying drawings and examples.
The example that the present invention tests is to be carried out so that grid voltage amplitude is uneven for condition；As shown in figure 1, the present invention exists
Synchronous inverter is incorporated into the power networks down, and the method being combined is led to caused by unbalanced source voltage with situation profit using Tendency Prediction
The unstable negative-sequence current of aggravation power network suppressed, reduce current unbalance factor, whole system is continually and steadily run；
It includes 1）Synchronous inverter is incorporated into the power networks control system：Synchronous inverter control module, inverter output end positive-negative sequence current/
Voltage decomposition unit, grid side power end positive-negative sequence voltage decomposition unit, synchronous inverter control module realize distributed power source
Access, can be incorporated into the power networks；Inverter output end positive-negative sequence current/voltage decomposition unit decomposes electric current, voltage parameter
For positive sequence and negative sequence component, it is input in corresponding positive-negative sequence control system, and mould is presented in the situation for establishing current unbalance factor
Block, to monitor negative-sequence current in real time with this influences variation tendency；Grid side power end positive-negative sequence voltage decomposition unit is by grid side
Voltage parameter is decomposed into positive sequence and negative sequence component, is input in corresponding positive-negative sequence control system, complete synchronous inverter and
Network control system；2）The Tendency Prediction method of system parameter during Voltage unbalance：Inverter output end current acquisition module, electric current situation
Identification and evaluation module, electric current Tendency Prediction model, the imbalance of voltage can cause the generation of negative-sequence current, synchronous inverter knot
CloseP-fWithQ-VTo realize voltage regulation and frequency modulation process, suppress unbalanced negative sequence component, be mainly reflected on negative-sequence current, therefore be
Parameter of uniting chooses inverter output current and carries out Tendency Prediction, and inverter output end current acquisition module is passed through using sensing element
Communication network by real-time Data Transmission into computer management system, as shown in Fig. 2 the current situation that this process is information carries
Take；Computer management system pre-processes to the data gathered, passage time association analysis, index of correlation is calculated, to this
Group data carry out Situation Assessment, judge which kind of forecast model it meets；The example that the present invention tests for grid voltage amplitude not
Balance uses Chaotic time series forecasting model；3）The systematic thinking way snobbish execution method led during Voltage unbalance：Current imbalance
Degree situation display unit, situation profit lead Rule of judgment setting module, condition threshold control negative phase-sequence controller switching, current imbalance
Degree situation display unit can directly reflect negative-sequence current situation of change, therefore the mark using current unbalance factor as condition judgment
Standard, the degree of unbalancedness of control electric current is in the scope of corresponding safety, you can suppresses negative-sequence current, it is too high to weaken current unbalance factor
And the problem of aggravating unbalanced source voltage；The setting of condition threshold need to consider time scale and the size of negative sequence current value, close
The threshold value setting of reason is to ensure the premise that negative phase-sequence controller is suited measures to differing conditions in terms of time.
The specific steps performed of Tendency Prediction method of the present invention is as follows：
1）Situation is extracted（Data acquisition）：Selection inverter output current is parameter, and system existst 1Moment starts voltage amplitude occur
Value is uneven, collectiont 1~t 2The data conduct of periodTData are pre-processed by the status information at moment, obtain required data
Collection is used as historical data；
2）Situation understands（Judge data characteristic）：Using gained historical data as time seriesi 1,i 2,...,i n Carry out mutually sky
Between reconstruction calculations relevant parameter and characteristic quantity（LyapunovIndex）To judge whether the time series has chaotic characteristic, judge
The method of chaotic characteristic has two kinds of intiutive analysis method and quantitative analysis method：
1. intiutive analysis method：Judge whether strange attractor；First using gained historical data as time seriesi 1,i 2,...,i n Be normalized, normalization formula is：；Then phase is carried out to the data after normalization
Space Reconstruction, i.e., by interval from time seriesτThe component fetched as vector, reconfigures out a collection of new vector（In formula：mFor Embedded dimensions；iFor the vector in the phase space after reconstruct,τTo prolong
The slow time；NFor the number of phase space vector after reconstruct,N=n-(m-1)τ；nFor the points of former time series）；Finally by
MATLAB softwares draw the phase space plan after reconstruct, as shown in Figures 3 and 4, according to can be straight with the presence or absence of attractor in figure
The chaotic characteristic for judging current time sequence is seen,
2. quantitative analysis method：CalculateLyapunovIndexλValue；Because each phase of current time sequence of extraction is one dimensional system
System, then defining one system of monophase current is：i n+1 =F(i), then itsLyapunovThe calculation formula of index is：（In formulaλFor maximumLyapunovThe value of index）Ifλ>0, then the time series have chaos special
Property, you can Tendency Prediction is carried out using Chaotic time series forecasting model；
3）Tendency Prediction：Foundation is based on improved maximumLyapunovThe multi-step Predictive Model of index, this model is in original calculation
Improved on the basis of method, multistep advanced prediction can be achieved, predict error within 10%,i 1,i 2,...,i n Phase space
Represent as follows：
In formula,mFor Embedded dimensions,τFor time delay, ifY M For forecasting centre's point,Y K ForY M Nearest adjoint point, thenλ 1For most
GreatlyLyapunovIndex, whereinY M+1Only last componenti n+1It is unknown, thereforei n+1It can forecast, then will predict what is obtainedi n+1Band
Enter to be input to forecast model as historical data in original data and can forecasti n+2, so iterating, it is pre- that multistep can be achieved
Survey；It is but maximum according to theory of chaotic dynamicsLyapunovIndexλ 1InverseT m =1/λ 1Represent chaos system deterministic forecast
Event horizon, i.e., most it is long it is pre- call time, therefore multi-step prediction step-length under certain precise manner is limited in scope, whereinT m AsT~T+1 time interval.
As shown in figure 5, current time sequence is respectively the current sequence that A, B, C three-phase change over time, in order that prediction
Precision is higher, and correlation analysis has been carried out to the result of prediction, usesFourierSeries, which is fitted, rejects singular point or bad
Data, the precision of prediction is substantially increased,FourierThe expression formula of series isf(x)=a 0 +a 1 cos(x*ω)+b 1 sin(x*ω)+a 2 cos(2x*ω)+b 2 sin(2x*ω)+..., the wherein selection of dimension is selected according to the error precision of fitting.
Situation profit guiding method of the present invention is carried out on the basis of Tendency Prediction, and its specific steps performed is as follows：
1）The situation of current unbalance factor is presented：It will predict what is obtainedT~T+1 period electric current situation valuei t ’,t=1,2,...,nBe future-state electric current as inverter output current actual value, positive-negative sequence is carried out to inverter output current further trend value
After decomposition, pass through calculation formulaObtain the value of current unbalance factor and pass through oscillograph
Carry out the variation tendency directly perceived for reflecting current unbalance factor, it is convenient to monitor current changing trend in real time；
2）Situation profit leads the setting of Rule of judgment：Presented by the situation of current unbalance factor, when monitoring current unbalance factor
During more than the threshold value being previously set, reach early-warning conditions, the measure of beginning to take on is controlled；Setting for threshold value, it can adopt
With Threshold Analysis method（threshold approach）；With reference to the treatment Threshold Analysis method in decision analysis, it thinks substantially
Want when a patient suspected suffers from certain sick probabilityPLess than treatment threshold value（therapeutic threshold）When, then do not give
Patient implements therapeutic scheme and implements follow-up observation；Conversely work asPDuring more than treatment threshold value, then it should make and give Case treatment
Determine；Similarly, when the current unbalance factor of synchronous inverter output current is less than threshold value, the control of grid side voltage is transported in safety
In line range, whole system running status is also not affected by threat, i.e., does not give treatment and be to continue with monitoring observation；When synchronous inversion
When the current unbalance factor of device output current exceedes threshold value, grid side voltage unbalance factor exceedes correlation standard value, electric current
Degree of unbalancedness also reaches early-warning conditions, need to then control it, that is, be given by negative phase-sequence control system to weaken negative-sequence current
The decision for the treatment of；
3）Negative phase-sequence controller active decision：When current unbalance factor reaches predetermined threshold value, condition judgment switch is switched to negative phase-sequence
Controller, negative phase-sequence controller is set to start to act on, it is suppressed that negative-sequence current, to reduce current unbalance factor；In view of due to synchronization
Inverter design virtual rotation inertia, makes system an inertia time be present, and this inertia time is the time of tabs under voltage
Constantτ v ≈K 0 /(ω*D q ), therefore predicted value needs to shift to an earlier dateτ v Moment import system, be not in just the situation of delay reflection；
, it is necessary to the time of forecast model be considered, if the time value is when in addition, to inverter output current progress Tendency Predictiont y , then whenT~T+The a certain moment in 1 periodT k Degree of unbalancedness exceed threshold value carry out negative phase-sequence controller switching when, its it is actual throwing
Cut predicted time and the habitual response time that the time should be the moment and subtract model, i.e. switching timeT 0 =T k -t y -τ v , so
It can guarantee that negative phase-sequence controller effectively acts on, to realize that effective situation profit is led, ensure that whole system can continually and steadily be run.
Above example is only that the synchronous inverter carried out is incorporated into the power networks situation when grid voltage amplitude occurs uneven
Sharp guiding method, and three kinds of situations of Voltage unbalance are required to consider, the selection of forecast model will be according to the characteristic of time series
To choose, but method provided by the present invention is not all departed from, the improvement for synchronous inverter and reasonable utilization, the present invention carry
A kind of method for effectively solving problem is supplied；It should be pointed out that on the premise of design spirit of the present invention is not departed from, this area
The various modifications and improvement that those of ordinary skill makes to technical scheme, it is true all should to fall into claims of the present invention
In fixed protection domain.
Claims (6)
1. synchronous inverter is incorporated into the power networks situation profit guiding method during a kind of Voltage unbalance, it is characterised in that：Including synchronous inversion
Device is incorporated into the power networks control system：Synchronous inverter control module, inverter output end positive-negative sequence current/voltage decomposition unit, electricity
Net side power end positive-negative sequence voltage decomposition unit；The Tendency Prediction method of system parameter during Voltage unbalance：Inverter output end
Current acquisition module, the identification of electric current situation and appraisal procedure, electric current Tendency Prediction model；Systematic thinking way is snobbish during Voltage unbalance leads
Execution method：Current unbalance factor situation display unit, situation profit lead the setting of Rule of judgment, condition threshold control negative phase-sequence control
The method of device active decision.
2. synchronous inverter is incorporated into the power networks situation profit guiding method, including following step during a kind of Voltage unbalance as described in requiring 1
Suddenly：
1）When Voltage unbalance occurs for grid side, synchronous inverter output voltage is not synchronous with grid side voltage, then inverter
To power network input current, grid side voltage and inverter output voltage, Current Decomposition are positive sequence and born using symmetrical component method
Order components, measurement obtain the amplitude and phase information of positive and negative sequence component；Simulation synchronous generator principle establishes positive sequence Synchronization Control
System and negative phase-sequence synchronous control system, wherein positive sequence synchronous control system realize the transmission of power, and negative phase-sequence synchronous control system exists
The regulation of voltage is carried out during Voltage unbalance；
2）During in Voltage unbalance, synchronous inverter is incorporated into the power networks, inverter is exported by current acquisition module first
Electric current carries out current situation extraction conductTThe status information at moment, secondly to extractionTTime data carries out situation identification with commenting
Estimate, that is, judge whether this group of data uneven trend occur（WithTThe current data being collected into before moment is compared analysis）
And data are pre-processed, judge data characteristic, forecast model is finally determined according to Situation Assessment result, then carry outT+When 1
The Tendency Prediction at quarter；
3）It will predict what is obtainedT~T+The actual value that the electric current situation value of 1 period exports as inverter, carry out coordinate transform and
The extraction of symmetrical components, and the situation of the value of calculating current degree of unbalancedness, i.e. current unbalance factor is presented；
4）Presented by the situation of current unbalance factor, threshold value setting is carried out to degree of unbalancedness, whenT~T+The a certain moment in 1 periodT k Degree of unbalancedness when exceeding this threshold value, the condition switch action of negative phase-sequence control system carries out active decision, negative phase-sequence controller
Start to act on, make the negative sequence voltage of synchronous inverter synchronous with the recovery of electrical network negative phase-sequence voltage, so as to suppress synchronous inverter output
Negative-sequence current, reduce current unbalance factor, ensure that whole system continues stable operation.
3. synchronous inverter is incorporated into the power networks situation profit guiding method during Voltage unbalance described in as requested 2, it is characterised in that：Institute
State step 1）In, for synchronous inverter according to synchronous generator operation principle, there is provided virtual rotation inertia, makes its dynamic response fast
Degree slows down, to maintain the inertia of power network so as to maintain the stable operation of power network, then realize inverter side and grid side voltage with
The synchronous operation of frequency, wherein synchronous inverter output end voltage equation expression formula are：（Formula
In：φFor rotating excitation field axis and the axis angle of A phases,M f For excitation mutual inductance,ɷFor rotor velocity,i f For exciting current）,
The stator terminal phase voltage of inverter is：（In formula：R l WithL l For stator winding coil resistance and inductance,iFor
Threephase stator electric current）；Run in equilibrium conditions when whole system starts, when line voltage occurs uneven, synchronous inversion
Device is to power network input currenti, i.e.,（In formula：R g WithL g For grid side line resistance and inductance,v g For power network electricity
Pressure,ɷ 0For electrical network angular frequency）, line voltage and inverter output voltage, electric current can be analyzed to positive sequence, negative sequence component（Because of synchronization
Inverter does not have the neutral conductor can not consider zero-sequence component）, then voltage unbalance factor be：, electric current
Degree of unbalancedness is：；Simulation synchronous generator principle establishes positive sequence synchronous control system and born
Sequence synchronous control system, wherein positive sequence synchronous control system by align sequence controller export voltage and frequency be adjusted come
Line voltage and frequency are tracked, so as to realize the transmission of active power and reactive power, negative phase-sequence synchronous control system running
In there is no the transmission of power, inverter output negative sequence voltage and electrical network negative phase-sequence voltage synchronous are only kept, by formula
Understand, whenu - =v g - When, havei - =0, this process is without influence on the operation of positive sequence synchronous control system, respective independent operating, because
This synchronous inverter suppresses in unbalanced source voltage to negative-sequence current, it is can be achieved in operational envelope
Synchronous inverter is incorporated into the power networks during unbalanced source voltage.
4. synchronous inverter is incorporated into the power networks situation profit guiding method during Voltage unbalance described in as requested 2, it is characterised in that：Institute
State step 2）In, current situation extraction is carried out to inverter output current by current acquisition module and is used asTThe state letter at moment
Breath, notei 1,i 2,...,i n BeTThe current time sequence at moment, because grid side Voltage unbalance has three kinds of situations, i.e. voltage
Amplitude is uneven, and unbalance in phase, amplitude and phase are all uneven, therefore the uneven situation of inverter output current also has three
Kind, in order that prediction effect is preferable, forecast model is according to three kinds of uneven situations respectively using chaos time sequence method, BP nerves
Neural network forecast method and wavelet neural network predicted method carry out Tendency Prediction；From the foregoing, it will be observed that needed before being predicted to extraction
Current time sequencei 1,i 2,...,i n Carry out situation identification and assessment, the i.e. unbalance factor of Cutoff current time series（Respectively
The characteristic quantity of forecast model）, it is predicted again after determining forecast model.
5. synchronous inverter is incorporated into the power networks situation profit guiding method during Voltage unbalance described in as requested 2, it is characterised in that：Institute
State step 3）In, it will predict what is obtainedT~T+1 period electric current situation valuei’(t),t=1,2,...,nBe future-state electric current
As inverter output current actual value, and the extraction of symmetrical components is carried out, corresponding current unbalance factor is calculated, passes through
The situation of current unbalance factor is presented to determine its development trend i.e. guiding of situation.
6. synchronous inverter is incorporated into the power networks situation profit guiding method during Voltage unbalance described in as requested 2, it is characterised in that：Institute
State step 4）In, byUnderstand, the degree of unbalancedness of grid side voltage directly influences inverter output current not
The degree of balance, by the system points of common connection of International Electrotechnical Commission's clear stipulaties（PCC）Normal voltage degree of unbalancedness permissible value is
2%, can be according to the degree of unbalancedness of grid side voltage in short-term no more than 4%, therefore when carrying out threshold value setting to current unbalance factor
Primarily determined that, i.e.,IUF=k 1 *VUF（In formulak 1For proportionality coefficient and）；If the time of forecast model ist y , because synchronous inverter is provided with virtual rotation inertia, slow down its dynamic responding speed, so in the presence of a habitual response
Timeτ v ≈K 0 /(ω*D q )（In formulaD q =-ΔQ/ΔVFor the sagging coefficient of voltage,ωFor electrical network angular frequency,K 0For time scale system
Number）, therefore work asT~T+The a certain moment in 1 periodT k Degree of unbalancedness exceed threshold value, when negative phase-sequence controller carries out active decision, its
The actual act time should be predicted time and the habitual response time for subtracting model at the moment, i.e. decision-making actuation time isT 0 =T k -t y -τ v , so just can guarantee that negative phase-sequence controller effectively acts on, to realize that effective situation profit is led, it is steady to ensure that whole system continues
Fixed operation.
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